The invention deals with a child's seat restraining system.
Such child's seat restraining systems are available in numerous embodiments. Essentially they consist of a child's seat which is fastened, either directly or indirectly by way of a frame, to the car seat by means of a two-point or three-point safety belt available in the automobile. The child is secured within the seat by means of a multi-point belt system, usually a four or five-point belt system.
Although such child's seat restraining systems are divided into groups where each group corresponds to a certain size or weight range, in practice tremendous size differences have to be bridged reliably, which is essentially done by adjusting the effective belt length. For example, child's seat restraining systems with four-point belts are known, whereby a waist belt and two shoulder belts are interconnected by means of a central buckle. Shoulder belts as well as the waist belt must be equipped with devices allowing adjustment of belt length. Belt deviating systems which are designed to increase friction by winding the belt around pins are the simplest devices of this kind. However, they are often difficult to adjust. Consequently, adjustment of the effective belt length, which is absolutely essential to meet the safety requirements based on the size of the child, is often not done at all, or at least not in the required manner.
EP 0 261 453 B 1 discloses a device for adjusting the belt length of a safety belt system wherein upon actuating a release control and overcoming a spring force, the belt can be unwound from the belt reel in order to obtain a greater effective belt length. When not actuated the reel is locked and the effective belt length is fixed. This kind of device for adjusting belt length is utilized, for example, on the shoulder belts of the above described child's seat restraining system with a four-point belt. It is intended that the effective belt length of these shoulder belts be increased before putting them on, and after they are put on, that the release control be actuated again whereby the spring action automatically pulls the excess belt length until the belt is as tight as determined by the spring force. This force is designed so that under normal circumstances, the resulting effective belt length is optimal.
This kind of belt length adjustment device is proven in practice. However, it is still felt disadvantageous that each shoulder belt must be equipped with a separate belt length adjustment device and that because of the exposed location of the device, the child himself can actuate it, which could lead to an unintentional lengthening of the effective length. An additional disadvantage is the fact that although the reel locks reliably because its angular movement is positively blocked, the remaining belt slippage around the blocked reel depends on the length of the wound up belt. Thus, the system with a fully wound reel contains more slack than the one with an empty reel.
Also known are child's seat restraining systems where the effective belt length of all belts is adjusted by a central adjustment device. The effectiveness of these systems depends largely on the force applied on the central adjustment device, which is a disadvantage.
DE 36 15 443 A1 discloses a child's seat restraining system with a central adjustment device located underneath the seat. Here the belt is indeed wound up and tensioned by a spring loaded reel, but the belt is arrested by mechanically locking the reel. This leads to belt slippage as the belt tightens around the reel under increasing load, especially when the reel is fully wound. This represents an increased safety risk, since the belt must be tightly strapped around the body, especially when the working load is applied.